Heres another question, the whole process relys on the heating...

Heres another question, the whole process relys on the heating of the granite by radioactive decay of (Uranium?) + I assume also because its gets hotter with depth.

So the rocks are host to a whole heap of daughter nuclides from the Uranium decay series, are or will any of these be leached from the rocks by the water, which being hot is going to be better able to leach material. And will any of these radioactive daughters then be liable to adhere or sorb onto the pipework, pumps or heat exchangers, slowly making them radioactive. That would definetly add to decommissioning costs. I have read I think on the threads some one mentionng that an assessment for radon gas problems had been made. But thats short lived and gasious, though dangerous, and not likely to scale.